CVE-2026-42845

The form plugin for Grav adds the ability to create and use forms. Prior to 9.1.0 , there is an unauthenticated page-content overwrite via file upload (GHSA-w4rc-p66m-x6qq). Public form uploads now strip path components from the POST-supplied filename and hard-block page-content extensions (md, yaml, yml, json, twig, ini) regardless of the configurable dangerous-extensions list. A permissive accept policy combined with the default destination: self@ could otherwise let an attacker overwrite the page's own .md and pivot to super-admin via a process: save action. This vulnerability is fixed in 9.1.0.